Pneumatic signal system



Fel.l 9, 1937. c. A. CAMPBELL 4 vPNEUMATIC S IGNAL SYSTEM Filed June 1o wi L @w Patented Feb. 9, 1937 UNTE STATES PATENT FME PNEUMATIC SIGNAL SYSTEM Application June 10,

Claims.

This invention relates to signal systems, and particularly to the Well known pneumatic systems used on railway trains.

As heretofore universally arranged such sys- 5 tems included on the locomotive a so-called signal pct or signal valve which was connected to the signal pipe extending throughout the train, and which responded to reductions of signal pipe pressure to blow a whistle by means of air derived from the Signal pipe itself. The signal pipe Was charged through a pressure reducing valve and a fixed orice located on the locomotive and not distant from the signal valve. Various cars were equipped With conductors signal valves, by means of which the signal pipe could be locally vented, thus initiating a reduced pressure wave which traveled through the signal pipe and affected the signal pot, causing the Whistle to blow.

Devices of this sort have been subject to seri- 20 ous limitations. The feed valve operated intermittently and created pressure Waves which conflicted with the Waves produced by the conductors valve so that blasts subsequent to the first were of diminishing strength and were occasionally obliterated entirely. The existence of pressure taper or pressure gradient in the signal pipe, which is occasioned by leakage greatly increased the difculty in securing satisfactory operation, and since the leakage increased with the pressure, recourse was had to low pressure operation, despite the fact that in the absence of pressure gradient the signal system would operate better at higher pressures.

As a result of tests it has been ascertained that the major cause of difliculties encountered in the operation of these signal systems, arises from the practice of feeding the signal pipe from the forward end. The purpose of the present invention is the elimination of the feed valve at the forward end of the signal pipe and the substitution of air feeding means on each car of the train, such means serving to supply air to the signal pipe at a restricted rate.

A convenient source of the feeding air is the brake system. In those brake systems in which local reservoirs are fed by the brake pipe one of the reservoirs on each of various cars may serve as the source of feeding air, preferably a reservoir not heavily drawn upon in service applications of the brake. In the case of the universal valves used on heavy passenger trains the emergency reservoir is a satisfactory source. In a single reservoir automatic system the well known auxiliary reservoir might be used, While on those systems in which a compressor is located on each 1935, Serial N0. 25,923

vehicle and each vehicle carries a .so-called main reservoir, this reservoir may serve as the source.

The invention will novv be described as embodied in conjunction With an automatic system of the type making use of relay valves, this system being selected because it isless familiar than the older systems which it bids fair to sup@ plant. Y

In the dravving,- j

Fig. 1 is a diagrammatic view of the brake system and related signal system cfa train made up of a locomotive and two cars.

Fig. 2 is a detail view, partly in section, of the feed connection.

On the locomotive there is a main reservoir Il), an engineers brake valve Il, assumed to be of the equalizing discharge type, and having an equalizing reservoir I2 and a feed valve I3. The brake valve II is connected to the brake pipe I4 which extends throughout the train andis connected from car to car bymeans of the flexible hose I5 and couplings I6. The usual angle cocks are indicated at Il.

On the locomotive and each car is a triple valve I8 which is connected to the brake pipe by a branch pipe I9. Connected to the triple valve is an auxiliary reservoir 2l and a volume reservoir 22. The triple valve operates in response to reductions of brake pipe pressure to establish a pressure in the volume reservoir 22 and in response to restoration of brake pipe pressure to exhaust the reservoir 22 and recharge the auxiliary reservoir. Interposed between the reservoir 22 and the brake cylinder or vcylinders 23 is a relay valve 24, Whose function is to act in response to the pressure established in the volume reservoir 22 to create a similar pressure in the brake cylinder 23. 'Ihe relay 24 derives its supply of air from a so-called local reservoir 25 which is charged from the brake pipe I4 through a check valve, not shown.

The brake system generally described has features of novelty, but they are not a part of the present invention and are not herein claimed. The purpose in illustrating this particular brake system is to indicate the general applicability of the feeding system forming the subject matter of the present invention. The essential point, so far as the signal system is concerned, is that the reservoir 25 is fed from the brake pipe I4 and is normally charged.

Leading throughout the train is a signal pipe 26 which is connected from car to car by flexible hose 21 and couplings 28. Cut out cocks 29 are indicated. On the locomotive the signal pipe is connected to the signal pot 3l which may be of any preferred construction familiar to those skilled in the art, and which functions on reduction of pressure in the pipe 26 to blow the signal Whistle 32.

Leading from the reservoir 25 on the locomotive and each car is a feed connection 33 to the signal pipe 26. Interposed in this connection is a combined check valve and strainer enclosed in the housing 34. Mounted in this housing are a strainer element .35 and two ball check valves 36 and 3l arranged in tandem, the purpose being to insure a tight seal by one of the valves should the other fail to seat tightly.

Also interposed in the connection 33 and beyond the housing 34 with reference to the direction of air flow, is a union 38 which encloses the choke 39. 'Ihe choke 39 limits the rate of flow through the connection 33. v

Mounted on each car (but not on the locomotive) is a conductors signal valve 4| which is connected to the signal pipe 26. This valve is conventionally indicated and `is of familiar form. It may be manually operated to vent the signal pipe 26, and when released closes automatically. The conductors valves for applying the brakes are indicated at 42 and may be manually oper-` ated to vent the brake pipe I4 to produce brake applications, as will be well understood.

The effect of the connections above described is to feed the signal pipe at substantially uniform pressures at spaced points throughout its length. Consequently the signal pipe is kept charged at uniform pressures and when a conductors signal valve is opened the reduced pressure wave thereby created may travel from end to end of the signal pipe without substantial opposition from the feeding connections. This arrangement permits the signal to be operated with absolute certainty and to be operated at almost unlimited number of times with certainty.

'Ihe reducing valve used to feed the signal pipe is entirely eliminated and all feed is supplied from the brake system. The signal pipe is operated at the relatively high brake pipe pressure instead of the relatively 10W pressure heretofore necessarily used when the signal pipe was fed from the forward end.

Another advantage of the system is that each car added to the train adds a properly proportioned feed connection so that the performance of the signal system is not so greatly affected by the length of train as it is when the signal valve feeding through a fixed orifice on the locomotive supplies all the air to the system.

Broadly considered, the invention contemplates the supply of airrat restricted rates and at substantially uniform pressures to the signal pipe at spaced points'throughout its length, irrespective of the source of the air. More specifically it contemplates feed from reservoirs forming part of a pneumatic brake system, and still more specifically, feed from the reservoirs of a brake sys-v closed valve operable to vent the signal pipe.

2. The combination of a fluid pressure train brake system includingra plurality of normally charged reservoirs located at intervals along the train; a signal pipe extending through the train; a signal device adapted to respond to reductions 0f signal pipe pressure; feed connections from said reservoirs to said signal pipe, said connections including flow restricting means, and means foi` preventing back flow; and at least one normally closed Valve operable to vent the signal pipe.

3. 'I'he'combination of a fluid pressure train brake system including a brake pipe and a plurality of reservoirs fed therefrom and located at intervals in the length of the train; a signal pipe extending through the train; a signal device adapted to respond to reductions of signal pipe pressure; feed connections from said reservoirs to said signal pipe, said connections each including flow restricting means and means for pre venting back flow; and at least one normally closed valve operable to vent the signal pipe.

4. 'Ihe combination of a train signal pipe; a signal device located adjacent Yone end of said pipe and adapted to respond to reductions of signal pipe pressure; at least one normally closed valve connected with said signal pipe at a point remote from said signal device and operable to Vent the signal pipe; and means connected with said signal pipe for supplying air to the signal pipe at substantially uniform pressure and at a restricted rate, at spaced points in the length of 1 the signal pipe, certain of the last named means being located nearer to said normally closed valve than to said signal device.

5. The combination of a signal device of the type adapted to be connected with a normally charged train signal pipe and to respond to re'- ductions of pressure therein; a train signal pipe connected with said device kand comprising a plurality of connected pipe units, such units each including a conductors valve operable to vent the unit; and charging means connected with each unit for supplying air to such unit at Aconstant pressure and at a restricted rate less than the venting capacity of said conductors valve.

CHARLES A. CAMPBELL. 

